Pope Francis on Monday publicly broached the prospect of his own death for the first time, giving himself "two or three years" but not ruling out retirement before then.

Talking to reporters on a flight back to the Vatican from South Korea, the 77-year-old pontiff, who seemed in good spirits, was asked about his global popularity, which was evident again during his five-day visit.

"I see it as the generosity of the people of God. I try to think of my sins, my mistakes, not to become proud. Because I know it will last only a short time. Two or three years and then I'll be off to the Father's House," he replied light-heartedly.